Quick Answer: The best gas tankless water heater for most homes is the Rinnai Sensei RX199iN — a condensing 199,000 BTU unit rated up to 11.1 GPM at a 0.98 UEF, with WiFi and a 15-year heat-exchanger warranty, at $1,530–$1,980 street, usually below the comparable Navien. Want instant hot water? The Navien NPE-240A2 has a built-in recirculation pump and a 15-year warranty. The Rheem RTGH-95DVLN and retail Rheem Performance Platinum 9.5 GPM are strong value picks, and the Takagi T-H3-DV-N is a strong mid-price condensing unit — though the Takagi brand itself was discontinued by the manufacturer on December 31, 2025, so it is now a closeout buy. Every GPM figure assumes a warm inlet — cold winter water lowers real flow.
Gas tankless water heaters deliver much higher flow than electric, which is why they’re the default for larger households, multiple bathrooms, and cold climates. We compared the top natural gas and propane units on flow rate (GPM), efficiency (UEF), warranty, and price — and separated the DIY-friendly retail models from the pro-installed lines so you buy the right one for your install.
By the numbers
- ~0.93–0.97 UEF for condensing gas units versus ~0.81–0.82 UEF for non-condensing, which is why condensing models vent through inexpensive PVC and cost less to run. — ENERGY STAR / DOE efficiency ratings
- 199,000 BTU rated up to 11.1 GPM on a flagship unit like the Rinnai Sensei RX199iN — enough to run 2–3 fixtures at once in most climates. — Rinnai
- 8–34% more efficient than a storage tank: the U.S. Department of Energy estimates on-demand heaters are 24–34% more efficient for homes using 41 gallons of hot water a day or less, and 8–14% for high-use homes. — U.S. Department of Energy
- 20+ years of typical service life for a tankless heater — more than double the 10–15 years of a storage tank, which offsets the higher purchase price over time. — U.S. Department of Energy
Our top picks at a glance
| Model | Best for | Type | Max Flow / BTU | UEF | Warranty | Price |
|---|---|---|---|---|---|---|
| Rinnai Sensei RX199iN | Best overall | Condensing | 11.1 GPM · 199k | 0.98 | 15 yr | $1,530–$1,980 |
| Navien NPE-240A2 | Best recirculation | Condensing | ~11.2 GPM · 199k | 0.97 | 15 yr | ~$1,850–$2,100 |
| Rheem RTGH-95DVLN-3 | Best price-to-BTU | Condensing | 9.5 GPM · 199.9k | ~0.94 | 12 yr | ~$1,500 |
| Takagi T-H3-DV-N | Best mid-price (closeout) | Condensing | 10 GPM · 199k | 0.93 | 15 yr | ~$1,558 |
| Rheem Performance Platinum 9.5 | Best retail/DIY value | Condensing | 9.5 GPM · 199k | ENERGY STAR | 12 yr | ~$1,150 |
1. Rinnai Sensei RX199iN — Best Overall
Rinnai Sensei RX199iN Condensing Gas Tankless
- 199,000 BTU condensing burner rated up to ~11 GPM — comfortably runs 2–3 fixtures at once.
- 0.98 UEF with inexpensive PVC venting; built-in Control-R WiFi.
- 15-year heat-exchanger warranty and typically $100–$300 cheaper than the Navien.
The RX199iN sits atop Rinnai’s condensing Sensei RX Series (above the entry RE and V lines) and is the gas unit we recommend to most homeowners. Rinnai rebranded this platform from RU199iN to Sensei RX199iN, lifting efficiency to a 0.98 UEF and stretching the heat-exchanger warranty to 15 years; remaining RU199iN listings are the same heater under the old name. One buying simplification that comes with the RX: its Adaptive Gas Valve runs on natural gas or propane out of the box, so there is no separate “iP” SKU to hunt down. We rank every current Rinnai — RX, RE, and V Series — in our best Rinnai tankless water heater guide.
2. Navien NPE-240A2 — Best With Recirculation
Navien NPE-240A2 Condensing Gas Tankless
- ComfortFlow built-in recirculation pump and buffer tank shorten the wait for hot water.
- Up to ~11.2 GPM at a 0.96–0.97 UEF — top-tier flow and efficiency.
- Class-leading 15-year heat-exchanger warranty.
Navien’s headline advantages are the built-in recirculation (which tames the “cold-water sandwich” and cuts the wait at distant taps) and the longest warranty here. If instant hot water and maximum coverage matter more than saving money, the NPE-240A2 is the one to get — retailer listings in August 2026 put it several hundred dollars above the Rinnai and Rheem picks here, not the near-parity pricing this guide showed at launch.
3. Rheem RTGH-95DVLN-3 — Best Price-to-BTU
Rheem RTGH-95DVLN-3 Condensing Gas Tankless
- Nearly 200,000 BTU and 9.5 GPM for meaningfully less than the Navien, and now tracking close to the Rinnai's low end.
- Condensing efficiency (~0.94 EF) with direct-vent PVC.
- Rheem's pro RTGH line — reliable and widely serviced.
The pro RTGH series is Rheem’s performance line (distinct from the retail Performance Platinum SKUs). The RTGH-95DVLN-3 gives you near-flagship BTU and 9.5 GPM well under the Navien’s current street price — the best price-to-BTU ratio in this roundup for a whole-home condensing unit. Rheem’s retail-vs-pro naming trips up a lot of buyers; our Rheem tankless lineup guide decodes every line, from the IKONIC flagship down to the electric RTEX series.
4. Takagi T-H3-DV-N — Best Mid-Price
Takagi T-H3-DV-N Condensing Gas Tankless
- 10 GPM and 199,000 BTU — strong flow for a family of 4–5.
- Condensing efficiency at a 0.93 UEF from a respected pro brand — note Takagi's own spec sheet lists this model as not ENERGY STAR qualified.
- 15-year heat-exchanger warranty.
Takagi is an A.O. Smith brand, not a Rinnai one — A.O. Smith bought Takagi’s U.S. assets and North American marketing rights in July 2010 for $5.5 million, per its fiscal-2010 Form 10-K. The T-H3-DV-N pairs 10 GPM with a 15-year heat-exchanger warranty and is now heavily discounted, around $1,558 against a $2,450 list. The catch you need to know first: the Takagi brand was discontinued by the manufacturer on December 31, 2025 per the notice on SupplyHouse’s Takagi pages, with parts available as supplies last. It is a genuine closeout bargain, not a long-term brand bet — we break down which units are still worth it and which A.O. Smith model replaces each one in our Takagi tankless water heater guide.
5. Rheem Performance Platinum 9.5 GPM — Best Retail / DIY Value
Rheem Performance Platinum 9.5 GPM (ECOH200) Gas Tankless
- Condensing 199,000 BTU, 9.5 GPM, ENERGY STAR certified with EcoNet WiFi.
- Convertible for indoor or outdoor installation.
- Sold at major retailers — the easiest premium gas unit to buy and get parts for yourself.
Rheem’s retail Performance Platinum “ECOH” line brings condensing efficiency, WiFi, and 9.5 GPM to the home-improvement aisle at the lowest price here. Don’t confuse it with the pro RTGH series — it’s the same idea packaged for retail buyers and DIY-friendly installs. It’s our value pick for a whole-home gas upgrade.
How to choose a gas tankless water heater
- Condensing vs non-condensing: Condensing (~0.93–0.97 UEF, PVC venting) costs more upfront but runs cheaper and vents cheaper. Non-condensing (~0.81–0.82 UEF) is cheaper to buy but needs stainless venting — see our condensing vs non-condensing comparison for the full installed-cost math.
- Size by GPM: Most 2–3 bath homes want 7–9 GPM at peak; a 199k BTU unit covers that in most climates. Cold inlet water lowers real flow, so size up in the North — our tankless water heater sizing guide has the full BTU/GPM formula and worked examples by climate.
- Natural gas vs propane: Buy the correct fuel SKU (or a convertible model) — they are not interchangeable without a conversion kit. On propane (LP)? See our best propane tankless water heater picks.
- Recirculation: Want instant hot water at far taps? Choose a unit with built-in recirculation (Navien) or plan to add a recirc line.
- Gas line & venting: A 199k BTU unit may need a 3/4” gas line and proper venting — see our gas line size guide for how BTU rating and run length set the actual pipe diameter. Get an installer to confirm before you buy.
The bottom line
For most homes, the Rinnai Sensei RX199iN is the best gas tankless water heater: 11.1 GPM, a 0.98 UEF, WiFi, a 15-year heat-exchanger warranty, and a $1,530–$1,980 street price below the comparable Navien. If instant hot water is the goal, the Navien NPE-240A2 adds built-in recirculation and a 15-year warranty. For the best value, the Rheem RTGH-95DVLN (pro) and Performance Platinum 9.5 GPM (retail) deliver near-flagship performance for less. Shopping the discontinued-brand bargains? Our Takagi guide and Bosch guide both cover what’s still worth buying on closeout — or see the brand that took the opposite path with a full 2026 refresh in our best Noritz tankless water heater guide. No gas line? See our electric tankless picks — or weigh the two in our electric vs gas comparison. Not sure a single unit covers your whole home? Our best whole-house tankless water heater guide picks by bathroom count and covers the twin-unit setup for homes that outgrow one flagship. On a tighter budget, Rheem’s own Home Depot-focused value brand delivers similar hardware for less — see our best Richmond tankless water heater guide for the non-condensing and condensing options and the shorter warranty tradeoff.